For several years, the growing volume of waste and in particular of household refuse has made it essential to seek solutions enabling this waste to be treated and utilized.
The use of such waste as fuel has already been thought of, but the presence in the latter of a high water content and of incombustible materials permits production only of insufficient energy.
In fact, such waste is constituted by a liquid phase containing only organic products and by a solid phase containing metallic, mineral and synthetic materials.
One solution consists in compacting the waste, and this makes it possible to obtain both residues dry enough to constitute a fuel offering an acceptable calorific power, and fluid substances which can be used, depending on their nature, in agriculture as soil improvement products or as raw materials from which chemical products can be extracted.
Devices are known already which make it possible to compress waste, which are generally constituted by hydraulic presses comprising a feed zone receiving the waste to be treated, a pressing chamber connected to means for recovery of the liquid phase and a chamber for discharge of the solid phase, situated downstream of the pressing chamber.
The pressing chamber comprises an intake aperture and an outlet aperture, and has a cross-section equal to that of a piston of a first jack.
The wall of the chamber comprises a multitude of perforations opening into a channel for discharging the liquid phase extracted by compression of the waste.
The outlet aperture of the pressing chamber is generally closed off by a plug carried by a rod of a second jack opposed to the first.
The pistons of the two jacks are movable alternately between a first position for compressing the waste and for discharging the liquid phase, during which the piston of the first jack enters the pressing chamber and the piston of the second jack seals the outlet aperture of said chamber, and a second position for discharge of the solid phase, during which the piston of the first jack continues its stroke and the piston of the second jack frees the outlet aperture of the pressing chamber.
However, presses of this type have disadvantages and in particular pose problems in maintaining leaktightness between the pressing chamber and the chamber for discharging the solid phase.
In fact, taking into account the substantial stresses generated at the moment of pressing of the waste, leaktightness is not totally provided at the level of the outlet aperture of the pressing chamber by the piston of the second jack, with the result that leaks of liquid may occur and enter the chamber for discharging the solid phase.
Moreover, the stroke of the piston of the second jack is relatively long. It corresponds to one thickness of the solid phase, i.e., for an imcompressible product, the equivalent of the length of the die, and this therefore necessitates a large oil capacity in order to actuate the jack. Taking this stroke into account, the response time of the second jack is relatively long and this does not enable high speeds to be obtained.